Burn-in apparatus having average voltage calculating circuit

ABSTRACT

A function test circuit inside a burn-in apparatus is mounted on a burn-in board and specifies a plurality of checked devices which operate normally. An average voltage calculating circuit calculates average voltage for test voltage applied to a plurality of checked devices specified on a mounting section. A voltage correction circuit receives the average voltage and outputs a control signal to control set voltage output from a device power supply generation circuit. Therefore, this burn-in apparatus can set the test voltage applied to the checked devices readily with high accuracy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a burn-in apparatus to perform aburn-in test for semiconductor integrated circuit devices.

2. Description of the Background Art

The burn-in test is performed in a checking process of semiconductorintegrated circuit devices. An object of the burn-in test is to removesemiconductor integrated circuit devices of potential early defect frommass-produced semiconductor integrated circuit devices prior toshipping.

FIG. 4 is a schematic block diagram showing a configuration of aconventional burn-in apparatus.

Referring to FIG. 4, the burn-in apparatus 100 includes a body 10 and aburn-in board 11. Body 10 includes a device power supply generationcircuit 12. Device power supply generation circuit 12 supplies setvoltage Vs to burn-in board 11 during the burn-in test. Set voltage Vswill be described below. Burn-in board 11 mounts a plurality ofsemiconductor integrated circuit devices to be checked DUTs (devicesunder test) (a semiconductor integrated circuit device is referred to asa checked device hereinafter). Each of a plurality of checked devicesDUTs is connected to device power supply generation circuit 12 via aprotective resistance element R1.

If any of a plurality of checked devices DUTs were broken during theburn-in test, protective resistance element R1 prevents the brokenchecked devices DUTs from affecting voltage applied to other checheddevices DUTs.

Therefore, when burn-in apparatus 100 applies test voltage V to each ofa plurality of checked devices DUTs, the set voltage Vs output fromdevice power supply generation circuit 12 is set as follows, consideringvoltage drop due to protective resistance element R1;

Vs=V+iR;

wherein i is a value of current consumption of each checked device DUTand R is a resistance value of protective resistance element R1.

The value of current consumption of checked device i would be different,however, depending on types of semiconductor integrated circuit devicesas checked devices DUTs, or on test conditions such as test rate duringthe burn-in test. As the result, set voltage Vs had to be set for everytype of checked device and every test condition.

In conventional burn-in apparatus 100, set voltage Vs was set manually.Thus, the frequent settings of set voltage Vs made the work loadheavier.

The value of current consumption of each checked device i would also bedifferent because of variations in manufacturing of respective checkeddevices DUTs. Therefore, the work load became heavier to improveaccuracy of test voltage V.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a burn-in apparatus ofwhich test voltage applied to checked devices can be set easily withhigh accuracy.

A burn-in apparatus according to the present invention includes aburn-in board, a device power supply generation circuit, an averagevoltage calculating circuit, and a voltage correction circuit. Theburn-in board mounts a plurality of checked devices. The device powersupply generation circuit supplies test voltage for a burn-in test to aplurality of checked devices mounted on the burn-in board. The averagevoltage calculating circuit measures the test voltage supplied to eachchecked device and outputs the average voltage. The voltage correctioncircuit outputs a control signal to control the device power supplygeneration circuit in accordance with the average voltage.

Thus the burn-in apparatus can set the test voltage in accordance withthe average voltage calculated in the average voltage calculatingcircuit.

The voltage correction circuit preferably includes a comparator. Thecomparator receives the average voltage and a predetermined voltage andoutputs the control signal.

Thus the burn-in apparatus compares the average voltage with thepredetermined voltage and controls the device power supply generationcircuit with this result. This can improve the accuracy of test voltageoutput from the device power supply generation circuit.

Furthermore, the burn-in apparatus preferably includes a sensing circuitwhich senses a plurality of checked devices mounted on the burn-inboard, and the average voltage calculating circuit measures the testvoltage supplied to each checked device sensed by the sensing circuitand outputs the average voltage.

Therefore the burn-in apparatus can measure the test voltage for thechecked devices mounted on the burn-in board. Consequently, the accuracyof set test voltage is improved.

Furthermore, the sensing circuit preferably senses two or more operablechecked devices among a plurality of checked devices.

Therefore the burn-in apparatus can sense the checked devices which aremounted on the burn-in board and are not broken by the test.Consequently, more accurate test voltage can be set.

It is preferred that the sensing circuit includes a function testingcircuit to perform a function test for a plurality of checked devices,and the average voltage calculating circuit outputs average voltage inaccordance with the result of the function test.

Therefore the burn-in apparatus can sense the checked devices mounted onthe burn-in board by the function test.

The average voltage calculating circuit preferably measures the testvoltage supplied to each of two or more checked devices among aplurality of checked devices and outputs the average voltage.

Therefore the burn-in apparatus can reduce the area required for wiringto measure the test voltage.

The burn-in apparatus according to the present invention measures forevery checked device the test voltage applied to the checked devices andcalculates the average voltage. The burn-in apparatus also corrects thetest voltage using the calculated average voltage. Consequently, theburn-in apparatus can set the power supply voltage applied to thechecked devices readily with high accuracy.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing a configuration of a burn-inapparatus in an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a voltagecorrection circuit in FIG. 1.

FIG. 3 is a flowchart showing an operation of the burn-in apparatusshown in FIG. 1.

FIG. 4 is a schematic block diagram showing a configuration of aconventional burn-in apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail withreference to the drawings. In the drawings, the same or correspondingparts have the same reference characters and the description will not berepeated.

FIG. 1 is a schematic block diagram showing a configuration of a burn-inapparatus in an embodiment of the present invention.

Referring to FIG. 1, the burn-in apparatus 200 includes a body 20 and aburn-in board 30 mounting a plurality of checked devices.

Burn-in board 30 includes mounting sections 1−n (n is a natural number)which mount a plurality of checked devices DUTs.

Mounting section 1 can mount m (m is a natural number) checked devicesDUT1-DUTm. Each mounted checked device DUT is connected to a devicepower supply generation circuit 13 inside body 20 via a protectiveresistance element R1. Each of a plurality of checked devices DUT1-DUTmmounted on mounting section 1 also receives test pattern signal outputfrom body 20. The test pattern signal will be described below. Mountingsection 1 includes a plurality of sockets (not shown) to mount aplurality of checked devices DUT1-DUTm.

Each of a plurality of checked devices mounted on mounting section 1 isalso connected to an average voltage calculating circuit 26 inside body20. Average voltage calculating circuit 26 will be described below.

A plurality of checked devices mounted on mounting sections 2−n are notconnected to average voltage calculating circuit 26. Otherconfigurations of mounting sections 2−n are the same as mounting section1 and the description will not be repeated here.

As the result, the number of checked devices mountable on burn-in board30 is n×m.

Body 20 includes a device power supply generation circuit 13, a functiontest circuit 21, an average voltage calculating circuit 26, a voltagecorrection circuit 27, and a control circuit 28.

Function test circuit 21 performs function test for a plurality ofchecked devices mounted on burn-in board 30. Function test circuit 21includes a timing generation circuit 22, a pattern generation circuit23, a driver and comparator 24, and a test result processing circuit 25.

Timing generation circuit 22 outputs a reference signal which will be abase for the function test. The reference signal output from timinggeneration circuit 22 determines a cycle time of the function test.

Pattern generation circuit 23 outputs a preset test pattern signal insynchronization with the reference signal output from timing generationcircuit 22.

Driver and comparator 24 outputs the test pattern signal to a pluralityof checked devices DUTs mounted on burn-in board 30. It also receivesthe signal output from each checked device DUT which received the testpattern signal, and determines whether the each checked device operatednormally or not, and then outputs the determination result to testresult processing circuit 25. Each of a plurality of checked devicesmounted on burn-in board 30 is specified, and the determination is donefor each checked device.

Test result processing circuit 25 stores the determination resultsoutput from driver and comparator 24. Test result processing circuit 25stores the determination results corresponding to a plurality of checkeddevices DUT1-DUTm.

Average voltage calculating circuit 26 receives the determinationresults stored in test result processing circuit 25, measures the testvoltage V applied to a plurality of checked devices which were mountedon mounting section 1 and operated normally, and calculates the averagevoltage Vave of the measurement results. Average voltage calculatingcircuit 26 outputs the calculated average voltage Vave to voltagecorrection circuit 27.

FIG. 2 is a circuit diagram showing a configuration of the voltagecorrection circuit in FIG. 1.

Referring to FIG. 2, voltage correction circuit 27 is configured with acomparator.

Referring to FIG. 2, voltage correction circuit 27 includes N-channelMOS transistors QN1, QN2 and P-channel MOS transistors QP1, QP2. Sourcesof transistors QP1 and QP2 are both connected to internal power node 40.Gates of transistors QP1 and QP2 are connected together and further,transistor QP1 is diode-connected.

Transistor QN1 has its drain connected to the drain of transistor QP1and transistor QN2 has its drain connected to the drain of transistorQP2, respectively. Sources of transistors QN1 and QN2 are both connectedto constant-current source 60. Reference voltage Vref is input to a gateof transistor QN1 and average voltage Vave is input to a gate oftransistor QN2, respectively, and control signal Vout is output fromoutput node A1 which is a connection point of transistor QP2 andtransistor QN2.

Reference voltage Vref is output from control circuit 28 which will bedescribed below.

Constant-current source 60 is connected to ground node 50.

Returning to FIG. 1, device power supply generation circuit 13 outputsset voltage Vs to supply test voltage V to a plurality of checkeddevices DUTs mounted on burn-in board 30.

In addition, device power supply generation circuit 13 receives thecontrol signal Vout and controls a value of test voltage V to be output.

Control circuit 28 stores a plurality of different burn-in testprograms. Control circuit 28 selects a burn-in test program and outputsto device power supply generation circuit 13 the information of testvoltage V to be applied to checked devices DUTs during the burn-in test.It also outputs the reference voltage Vref corresponding to the selectedburn-in test program to average voltage correction circuit 27.

An operation of burn-in apparatus 200 having the above-mentionedconfiguration will now be described.

FIG. 3 is a flowchart showing an operation of burn-in apparatus 200shown in FIG. 1.

Referring to FIG. 3, control circuit 28 in burn-in apparatus 200 firstselects a test of test NoT=1 (step S1). Herein, test NoT (T is a naturalnumber) indicates a number for each of a plurality of different burn-intests performed in burn-in apparatus 200. Burn-in apparatus 200 performsburn-in test of every test No for a plurality of checked devices DUTsmounted on burn-in board 30. Programs of multiple burn-in tests havingtest NoT are stored in a hard disk (not shown) inside control circuit 28of FIG. 1.

In step S1, control circuit 28 instructs device power supply generationcircuit 13 to supply test voltage V which will be applied to eachchecked device DUT for test No 1. Test voltage V is preset for everytest No and the data of the test voltage V for each test No is prestoredin hard disk inside control circuit 28.

Burn-in apparatus 200 then performs a function test for a plurality ofchecked devices DUTs on burn-in board 30 (step S2). The function testis, for example, a march pattern test.

At this time, function test circuit 21 outputs test pattern signal.Furthermore, it uses signal output from each checked device DUT that hasreceived the test pattern signal to determine whether each checkeddevice operated normally or not, and stores the results in test resultprocessing circuit 25 inside function test circuit 21. With theoperation of step S2, burn-in apparatus 200 can specify the checkeddevice DUT which is mounted on burn-in board 30 and is not broken.

Then, device power supply generation circuit 13 outputs set voltage Vsto apply test voltage V to each checked device DUT. Average voltagecalculating circuit 26 inside burn-in apparatus 200 measures the testvoltage V actually applied to checked devices DUTs using thedetermination results stored in test result processing circuit 25 (stepS3).

More specifically, average voltage calculating circuit 26 obtainsdetermination results of a plurality of checked devices DUT1-DUTm onmounting section 1 from test result processing circuit 25. From theobtained determination results, average voltage calculating circuit 26specifies a plurality of checked devices DUTs which are mounted onmounting section 1 and operated normally. Then, average voltagecalculating circuit 26 measures test voltage V applied to a plurality ofchecked devices DUTs which are specified.

Thereafter, average voltage calculating circuit 26 calculates averagevoltage Vave of test voltage measured in step S3 (step S4). Averagevoltage calculating circuit 26 outputs the calculated average voltageVave to voltage correction circuit 27.

Voltage correction circuit 27 receives the average voltage Vave andoutputs the control signal Vout (step S5). Reference voltage Vref isoutput from control circuit 28 and the value differs for every test No.Voltage correction circuit 27 outputs control signal Vout to devicepower supply generation circuit 13.

Device power supply generation circuit 13 then determines whether thevoltage value of received control signal Vout is within tolerance or not(step S6). Tolerable range of control signal Vout is prestored in devicepower supply generation circuit 13.

If the determination result of device power supply generation circuit 13indicates that the received control signal Vout is within tolerance,burn-in apparatus 200 will perform burn-in test of test No 1 (step S7).

After the test is completed, control circuit 28 selects test NoT=2 (stepS8), and burn-in apparatus 200 restarts the operation from step S2.

On the other hand, if device power supply generation circuit 13determines that the received control signal Vout is out of the tolerancein step S6, device power supply generation circuit 13 corrects setvoltage Vs corresponding to control signal Vout (step S9). Correctionamount of set voltage Vs corresponding to control signal Vout isprestored in device power supply generation circuit 13, and device powersupply generation circuit 13 corrects set voltage Vs based on thecorrection amount determined with received control signal Vout.

After the correction of set voltage Vs in step S9, the operation ofburn-in apparatus 200 returns to step S3. Correction operation of stepS9 will be repeated until the voltage level of control signal Voutoutput from voltage correction circuit 27 is included in the tolerance.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A burn-in apparatus, comprising: a burn-in boardon which a plurality of checked devices are mountable; a device powersupply generation circuit supplying test voltage for burn-in test tosaid plurality of checked devices mounted on said burn-in board; anaverage voltage calculating circuit measuring said test voltage suppliedto each of said plurality of checked devices and outputting an averagevoltage; and a voltage correction circuit outputting control signal tocontrol said device power supply generation circuit in response to saidaverage voltage.
 2. The burn-in apparatus according to claim 1, whereinsaid voltage correction circuit includes a comparator receiving saidaverage voltage and predetermined voltage and outputting said controlsignal.
 3. The burn-in apparatus according to claim 1, furthercomprising a sensing circuit sensing said plurality of checked devicesmounted on said burn-in board; wherein said average voltage calculatingcircuit measures said test voltage supplied to each of said plurality ofchecked devices sensed by said sensing circuit and outputs said averagevoltage.
 4. The burn-in apparatus according to claim 3, wherein saidsensing circuit further senses two or more operable checked devicesamong said plurality of checked devices.
 5. The burn-in apparatusaccording to claim 4, wherein said sensing circuit includes a functiontesting circuit performing a function test for said plurality of checkeddevices; and said average voltage calculating circuit outputs saidaverage voltage in response to the result of said function test.
 6. Theburn-in apparatus according to claim 1, wherein said average voltagecalculating circuit measures said test voltage supplied to each of twoor more checked devices among said plurality of checked devices andoutputs said average voltage.